Electron Configuration Basics

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Quantum Mechanics Noun

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[kwon-tuhm mi-kan-iks]

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Quantum Mechanics

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A branch of physics describing the behavior of matter and energy at the subatomic level, essential for understanding electrons.

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Example: This diagram shows the quantum model of an atom, where electrons exist in a 'cloud' of probability around the nucleus, not in fixed orbits.

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Bohr Model Noun

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[bor mod-l]

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Bohr Model

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A simplified atomic model that depicts electrons orbiting the nucleus in specific, fixed energy levels or shells.

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Example: This diagram shows the Bohr model of an atom, with a central nucleus (protons and neutrons) and electrons orbiting in distinct energy shells.

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Principal Energy Level Noun

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[prin-suh-puhl en-er-jee lev-uhl]

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Principal Energy Level

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The main energy shell of an electron, designated by the number 'n', indicating its average distance from the nucleus.

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Example: This diagram shows an atom's electrons arranged in distinct shells, or principal energy levels, with the first level holding 2, the second 8.

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Sublevel Noun

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[suhb-lev-uhl]

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Sublevel

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A subdivision within a principal energy level, containing one or more orbitals and designated by letters s, p, d, or f.

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Example: This diagram shows that main electron shells are made of smaller energy sublevels (s, p, d, f), with each sublevel having a specific energy.

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Orbital Noun

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[or-bi-tl]

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Orbital

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A specific region within a sublevel that has a high probability of containing an electron, holding a maximum of two.

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Example: An orbital is a 3D region around an atom's nucleus where an electron is likely to be found; they have different shapes, like spheres (s-orbitals).

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Aufbau Principle Noun

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[owf-bow prin-suh-puhl]

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Aufbau Principle

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The rule stating that electrons fill the lowest available energy orbitals before occupying any higher energy orbitals in an atom.

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Example: This diagram shows the order in which electrons fill orbitals, starting from the lowest energy level (1s) and following the diagonal path.

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Pauli Exclusion Principle Noun

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[paw-lee ik-skloo-zhuhn prin-suh-puhl]

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Pauli Exclusion Principle

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The principle that an orbital can hold a maximum of two electrons, and those two electrons must have opposite spins.

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Example: This diagram shows that when two electrons share an orbital (the box), they must have opposite spins (one arrow up, one down), as shown by the checkmark.

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Electron Spin Noun

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[i-lek-tron spin]

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Electron Spin

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An intrinsic quantum property of an electron that can have one of two opposite values, often called spin-up or spin-down.

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Example: An electron acts like a tiny magnet and can spin in one of two opposite directions, called 'spin up' or 'spin down'.

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Hund's Rule Noun

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[hunds rool]

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Hund's Rule

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The rule stating that electrons will singly occupy each orbital in a sublevel before any orbital is doubly occupied.

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Example: This diagram shows how electrons fill separate orbitals (boxes) with the same spin (up arrows) before pairing up, which is the basis of Hund's Rule.

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Degenerate Orbitals Noun

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[di-jen-er-it or-bi-tls]

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Degenerate Orbitals

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A set of orbitals that are in the same sublevel and therefore have the exact same energy level.

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Example: This diagram shows that some electron orbitals, like the three '2p' orbitals, are at the same energy level, which is what 'degenerate' means.